Central heating: overview and numbers

Here's the last of the central heating info - we haven't had a power bill yet so will update with approximate running costs when we get that, but for now I thought I'd summarise what we think and how much it cost.

The highly attractive heating unit, just after we started the ducting

The system we chose is the Rinnai iHeat. It's a ducted system, so blows warm air into the rooms. The air is warmed by water from the Infinity water heater we installed (which will also eventually serve both bathrooms and the kitchen).

Pros:

• Keeps the whole house warm when we have the system turned on
• Warms the house up pretty quickly (much quicker than a heat pump or fire)
• Cheapest option for whole-house heating
• Ceiling vents are unobtrusive
• Very quiet
• Efficient (and hopefully cheap to run!)

Cons: 

• Blown air is not quite as nice as radiant heat
• Can't control zones separately - one thermostat for the whole house

We have made a few tweaks to improve performance, and have a couple of other things we're planning to do in the longer term as well. 

Behold the button-thing, by which the vents may be adjusted

Firstly, balancing is part of the set up, but basically just means varying how open the vents are. Each vent has a button-thing (technical term) in the middle which allows you to adjust flaps inside the grill. The flaps can be mostly closed (so almost no air flows through) or fully opened (so as much as possible comes in). To balance the system, i.e. try to get all the rooms evenly heated, you start with the rooms furthest away from the heating unit, fully opening their vents, and then work back towards the centre of the house, with the more central vents being progressively more closed. 

Despite balancing, the airflow downstairs isn't as good. There are three ducts for downstairs; one in our son's room; one in our room; and one in the future bathroom. The one in our son's room works pretty well, but is poorly located above the door. Since his door gets closed when he's napping, which is when it most needs to be warm, it works okay, but we'll monitor that for a while and may eventually move the vent. 

Our bedroom is served by a poorly installed piece of flexible ducting, adopted from the HRV. Our room is the least accessible, ducting-wise, so we plan to eventually (before next winter!) get a length of rectangular plastic ducting to replace the dodgy old stuff. Because it's a straight run but we don't have good access between the rafters to smooth out the flexible ducting we think this will make a big difference. 

The bathroom vent is currently capped, because the bathroom doesn't even have walls and we're not really interested in paying to heat the dirt under our house. Once the bathroom has been built and that vent is in action we imagine the downstairs will become a bit more temperate, but in the meantime we've still got a heat pump down there for colder days (it's probably been turned on - briefly - three times in the past two weeks). 

We noticed immediately after it was turned on that the roofspace was very hot when the system was running, and realised that some gaps in the metalwork of the heating unit meant heat was escaping unnecessarily. I rang Rinnai to check if we could stop up these gaps, and they said that was no problem, so long as we used an appropriately heat-rated silicon sealant - so out came the caulk gun and now hopefully we're not leaking money into the attic. ;-) 

Another possible future tweak is the addition of a damper so we could turn off rooms not in use. These can be operated by a wall switch and can close off a branch of the system. The advice on this is a bit conflicting - our gasfitter said the iHeat's computer would shut down if we used one, as it would detect the damper as a blockage in the system, but Rinnai's info says they can be used. We'll see how the running costs look and then potentially do more research on that one.

The position of the thermostat is the subject of some discussion - it's in the warmest area of the house, which is not ideal, but it is conveniently located... So again we're going to wait and see. Installation consisted of poking a bit of cable down the wall and plugging the wall unit into it, so if we decide it would be better somewhere else we just need to fish the cable out and dangle it down a different wall. 

Overall we're very happy - the thermostat is quite programmable, so it turns on before we get up in the morning and turns itself off at bedtime, and we are magically kept warm without even thinking about it. You can easily turn it off if you're leaving when it's programmed to be on, and you can increase the temperature and/or fans temporarily if you're feeling particularly cold. 

And the cost - well, it's a big outlay, yes, but overall not too bad considering the outcome. For us, well worth it. If you're looking for something similar but don't have reticulated gas available in your area I'd encourage you to look into heat pump central heating - slightly more expensive but still a lot more reasonable than a furnace system! 

Costs:

System install (Infinity water heater and iHeat system, including commissioning) - $10,547.88

Extra vents - $184.71

Electrical work - power to the Infinity and iHeat units, decommissioning heat pump - $500 (approx)

RJ45 cable and connector for thermostat - $16.80

Cable ties - $92

Recovered $$$ from sale of both HRVs and one heat pump (less Trademe fees) -  -$1748.27

Central heating installation

Budget: $10,000

Timeframe: 6 weeks (mostly waiting for gas to be hooked up)

Who did the work: Us (4 days), gasfitters (1.5 days), sparkies (half a day)

Actual cost: $9,593.12

Learnings: Installing ducting isn't very hard, though it is a bit unpleasant spending a lot of time crawling around in attics. Pay attention to how things are working after installation as small tweaks can make big improvements in performance and efficiency. 

Central heating - running the ductwork

Our gas got hooked up a week ago, which means we've had seven blissful days of a temperate, evenly heated house. 

Before that could happen we had to run the ducting, as part of the deal we struck with the gasfitter. This took us a few days - partly because our work is often interrupted by a small person, and partly because we hadn't done it before so were working things out as we went. 

The first, doubtful join

The first snafu was on the very first join. We put the small one down for a nap, climbed into the roofspace, got the duct tape out... And second-guessed ourselves. The gasfitter had given us a quick lesson on how to tape the ducts up when he brought the kit around, but we wanted to refresh ourselves. So we googled. And (possibly for the first time ever), it wasn't helpful. 

Ducted central heating is most common in the United States - but all the US videos we found recommended against using duct tape, instead suggesting mastic glue and cable ties (the adhesive on the tape softens when exposed to heat, meaning the tape can let go when the system is in use). However, the videos all used metal junctions (ours are plastic) so we weren't sure if the advice translated to us. 

After a bit of (read: extensive) discussion and a chat to the gasfitter (who stood by the use of tape only) we decided we would get some cable ties, and use them with the tape for good measure. 

(aside: it seems ridiculous calling them "cable ties" when they are wrapped around a 350mm diameter duct, but - correct me if you know otherwise - that seems to be the term used here. I guess sometimes bunches of cables might get that large?)

Once we got into it, running the ducting was pretty simple: the objective is to keep the runs as straight and smooth as possible, so a little bit of thinking ahead is advisable. Though not what we did, with the benefit of hindsight I'd recommend laying out as many ducts as you can to see where they sit before connecting any. As well as trimming the ducting to length, hanging bendy bits (e.g. where it joins the ceiling vents) to ease the angle of the bend is recommended. 

This is a mostly-done shot - we hadn't finished hanging the ducts yet.
It's very hard to get good shots of how they run because everything's a bit crowded up there.

We were hoping we might be able to reuse some of the ceiling vents from the HRV, but these weren't ideally placed; most of them were close to doorways, and the heating vents are supposed to be as close to the outside of the room as possible. We have reused one upstairs, in the dining room / kitchen, which has three vents in total so one in the middle made sense, and currently both downstairs bedrooms are using the HRV holes, because we were loath to cut new holes in the recently painted, good condition gib... But we'll see how performance goes and move them if we need to. 

The trickiest part of vent placement is working out where they can sit - that job really needs two people, so one person can check out location in the room and the other can check for joists etc in the roofspace above. We did a bit of knocking and talking to try to roughly work out where we were, and then I would drill a hole from below in the centre of the proposed vent hole. My husband would then check from his side that the hole wouldn't hit anything and if it was good I'd draw a circle (the vents came in boxes which included a template, very helpful, though we could have made our own). 

Once the hole is there you poke the duct down through it, tape/cable tie on the vent, and push it into the hole. We also had to do a bit of jiggery-pokery (technical term) on a few of the holes, as our old house has several double ceilings so the clips on the vent didn't always work as perfectly as they ought. 

We also had to construct a return air duct - basically a chimney which takes the cooler air back up to be heated again. This has to be central (and is a large part of why the outlets need to be on the outside) so has consumed a large part of our hall cupboard. Our box is built out of MDF and chipboard; MDF on the visible side, for a good paint finish, and chipboard because we had a lot of it going to waste and it will do just as good a job. The most important functional outcome was for the box to be airtight, so plenty of sealant has been applied to all the joins. 

Because we would have boxed it in anyway we chose to build the box to the top of the cupboard and attach the duct at ceiling level, rather than ducting from lower down.

The inlet vent, which is mounted on the size, sits in a nice, snug hole - it has to be removable so the filter can be cleaned, so the lesson here is measure twice, cut once! Once the wall had a hole in it we cut pieces of MDF to line the cavity so the air goes into the box rather than up the wall. 

This is the least pretty part - the big return air vent - but it's no worse than a heat pump... I guess most heating systems have ugly bits.

We're pretty happy with how it runs - we're still fine-tuning a little but it's glorious to get up to a warm house... We are keen to see our first gas bill though!

I'll share a bit more about the pros and cons, the fine-tuning process and costs next week... Stay tuned!

Keeping warm - the central heating edition

We are a day away from firing up our very own central heating system. It's a very un-Kiwi way of heating a home, but one that we hope will be both comfortable and efficient. I'll come back to how it works for us once it's up and running, but I wanted to share why we've chosen a central heating system instead of say, a heat pump or a fire.

When we moved into our house, it had two heat pumps and two HRV systems - one of each on each level. Both heat pumps did a good job of heating the rooms they were in. Unfortunately, the downstairs one is in our bedroom, which we prefer on the cool side anyway - 16-18 degrees is about right for sleeping, I reckon, so not much heating needed. Upstairs it was in what would have been the dining/living room for the previous owners, but will be dining/kitchen for us. Useful, but it leaves our lounge, the other three bedrooms, two bathrooms and hallway out in the cold.

And as for the HRVs - well, they did remove moisture from the air, but as I've written before, I'm not sold on the benefits of those systems; I prefer to minimise the moisture that ends up in the air and use the high-tech apparatus known to those in the trade as "windows" for ventilation.

We knew we'd have to do something about heating those extra spaces but it wasn't the immediate plan... Until we got into hot water.

Because we're adding a bathroom downstairs we knew we'd need some extra water heating at some stage, and since we're in the midst of relocating the kitchen, which (who knew?) involves plumbing, it made sense to look at water heating now, so that we don't end up running a whole bunch of new pipes and then needing to move them in a year or so.

So we started investigating our options. As well as the water heating, we had three distinct problem zones for heating: our son's downstairs bedroom (which bears the brunt of the bitter southerly, straight off Cook Strait); the new lounge; and the two upstairs bedrooms. We went through a lot of different options, which all had complex costs and benefits associated. So we did what anyone would do; we made a spreadsheet.

All the coolest people run their life with spreadsheets

As you can see, all of the options we came up with were pretty costly. The cheapest option was about $7k, and that didn't serve the whole house very well. The top of the range isn't really shown here because we only looked at cheaper central heating options - I'm sure a radiator system would have taken us well over the $20k mark. 

Having read a bit about it before we got the quote, we had high hopes that the gas central heating system might come in at a reasonable price. It's a newish system (Rinnai iHeat) which works off the Rinnai Infinity water heater, which means the water heating cost is bundled into the total.

Disappointingly, at just shy of $14k it was well over our $10k budget. And then my husband had a stroke of genius: what if we were to run the ducting ourselves? We suggested it to the gasfitter and he agreed that might be a good option. We're grateful that he was pragmatic*, because when the quote came back it was nearly $3k cheaper, which made it make sense for us (not to mention that we do quite enjoy the DIY malarkey and find it more satisfying to be part of the process and understand how it all works).

It's more than we were planning to spend on heating in the short term, but it makes more sense to do it now than having to patch heat pump holes in our freshly painted walls in a year or two - and we should get over $1000 back by selling the heat pumps and HRVs. So net cost should be a smidge under $10,000. 

The moral is: it's expensive, but actually not that crazy if you have several areas in your home that need heating. And for goodness' sake if you're thinking of installing two heat pumps and two HRVs think about whether central heating might make more sense! We feel quite sad that the previous owner spent all that money for very localised comfort when he could have had the whole house toasty.

Have you ever thought about getting central heating? If you have it, how do you find the running costs?



* understandably many tradies don't want DIY wannabes like us doing half the job, lest we try to blame them for our own ineptitude

Keeping warm - the ventilation edition

It's been a bit quiet around here as I'm struck down with some kind of horrible lergy - but I did manage a bit of fossicking around in the attic today before I crawled back into bed - you know how when you're sick the first dose of paracetamol often makes you think you're actually okay until you get knocked off your perch mid-morning? So anyway, no photos or real progress to speak of but we've been learning lots about heating and ventilation so I thought I'd share a bit about the latter.

Our house came equipped with two HRV systems. I know this will excite some people - and perhaps in some houses HRV systems are worth having, but I am not sold. Ventilation is good, yes, but several thousand dollars is a big outlay for something that only somewhat dries out the air.

That's a bit beside the point when someone has already put the systems in, though, so we thought we'd give it a whirl. Well, we've been here for two months now, and used the HRVs for the first month (maybe a bit more) while we worked out what to do about heating (there were two heat pumps, but they only heated the rooms they're in, leaving the rest of the house pretty cold).

We've now decided on our heating solution (a reasonably uncommon option for Kiwis - ducted gas central heating - more on that soon as we're in the process of installing the ducting ourselves) and have had a bunch of electrical work done, including having the HRVs removed. Have we noticed a difference? Not really.

We're well aware that ventilation is very important for a healthy home - and lacking in many NZ houses, probably mainly because they feel so cold - but there are other ways to achieve that.

The best way to ventilate, and cheapest by a long shot, is to throw open the windows - as many as possible, in particular those which will catch the cross wind - for 10-30 minutes once a day. Yep, those minutes will be a bit chilly in winter, but a dry house is healthier and easier to heat. Once you've closed 'em up again crank up your heating and it'll warm back up in no time.

If your house is particularly damp (i.e. if you notice a lot of condensation on the windows or walls) you might need to take more targeted action.

The first thing is to avoid putting moisture into the air if possible. Just breathing adds some moisture but don't stop doing that! But there are three main culprits, all of which are reasonably easily solved:
1. Cooking 
Make sure you have a good rangehood over your hob (and that you use it!), and keep lids on pots as much as possible when cooking.
2. Showers
Install a fan in your bathroom if there's not one already - if possible add it to the same circuit as the lights with a delay timer so it runs for a while to clear steam after a bath or shower.
3. Drying clothes
If possible, dry your clothes outside on the line. If you have a dryer, duct it! This is pretty easy to do - you can buy ducting kits from hardware stores and appliance stores, add a couple of hours of your time (or pay a handyman if you're able) and you're all sorted. Here's the bit I only learned recently - if you can't dry your clothes on the line outside you are better off putting them into a ducted dryer than hanging them on an airer inside. You'll likely use more energy getting the water out of your house than you would have done running the dryer.

The small droplet symbol on the
left shows it's on the right mode

Okay - got prevention covered but still damp inside? If you have a heat pump, try running it on the dehumidifying mode for a few hours next time you're out. This only works when it's cooling so it will reduce the temperature, but does an okay job at removing moisture at a pretty low cost. In our old house we did this for about three hours once every couple of weeks in winter, which was enough for us (we actually probably wouldn't have needed to do that I'd learnt the bolded bit above about the dryer a bit sooner).

Freestanding dehumidifiers are even better at drawing out the moisture, so if you're really struggling to keep the walls dry, buying or borrowing one of those and moving it around the rooms of your house should do the trick.

By all means if these things don't solve your problems maybe look into a ducted ventilation system - but please try the cheaper things first! You might be surprised. :-)

Back to our disaster house new home - there was no extraction at all in the kitchen when we moved in, and no outdoor clothesline or dryer ducting. So I'm thinking the previous owner may have jumped the gun a little on the HRVs... Oh, and there is a little moisture issue at the back of the house where the back wall of the laundry is actually the concrete retaining wall - that one will be a bigger problem for us to solve a wee way down the road... Not looking forward to that!

Have you lived in a horribly damp house? Do you have any tips to add?